The present invention relates to in plant power distribution centers such as motor controllers and particularly relates to operating mechanisms for contactor assemblies which are interlocked. Most particularly the invention deals with interlocked mechanisms used to prevent closure of contactor assemblies under certain conditions.
Motor controllers having interlocked contactor assemblies are known in the art for a large variety of both interlock functions and interlock mechanisms to achieve those interlocked functions. Often in a motor control center, the motor control center will include a contactor capable of making and breaking the normal design motor loads and a hand actuated disconnect switch which interrupts the power supply to the contactor under an essentially no load condition. Either the contactor or the disconnect switch may be interlocked with a door to a sheet metal enclosure of the motor control center to prevent the opening of the door when power is supplied to the load or the contactor or both. When the contactor is supplied power through a disconnect switch which is only capable of disconnecting the power mains under essentially a no load condition, the disconnect switch is usually prevented from opening by a interlock mechanism between the contactor and the disconnect switch which prevents the switch from opening when the contactor contacts are closed. These mechanisms are subject to considerable stress as a result of the contactor closing and opening, and as a result the desired interlock function can degrade over time.
Among the publications relating to operating mechanisms are the following typical U.S. Patents assigned to the assignee of the present invention Square D Company.
U.S. Pat. No. 4,612,424 issued to Michael R. Clark et al on Sep. 16, 1986 describing a DOOR MOUNTED CIRCUIT BREAKER OPERATING APPARATUS.
U.S. Pat. No. 4,598,183 issued to Jeffrey B. Gardner et al on July 1, 1986 describing a TRIP INDICATING CIRCUIT BREAKER OPERATING HANDLE.
U.S. Pat. No. 4,090,230 issued to Frederick B. Fuller et al on May 16, 1978 describing a HIGH VOLTAGE MOTOR STARTER ENCLOSURE.